首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   65710篇
  免费   921篇
  国内免费   541篇
测绘学   1889篇
大气科学   4879篇
地球物理   13268篇
地质学   22688篇
海洋学   5688篇
天文学   14906篇
综合类   168篇
自然地理   3686篇
  2021年   558篇
  2020年   607篇
  2019年   699篇
  2018年   1552篇
  2017年   1489篇
  2016年   1847篇
  2015年   1043篇
  2014年   1756篇
  2013年   3306篇
  2012年   1946篇
  2011年   2566篇
  2010年   2275篇
  2009年   3050篇
  2008年   2687篇
  2007年   2681篇
  2006年   2561篇
  2005年   1915篇
  2004年   1945篇
  2003年   1773篇
  2002年   1818篇
  2001年   1651篇
  2000年   1577篇
  1999年   1324篇
  1998年   1293篇
  1997年   1370篇
  1996年   1094篇
  1995年   1053篇
  1994年   1031篇
  1993年   860篇
  1992年   798篇
  1991年   794篇
  1990年   787篇
  1989年   776篇
  1988年   717篇
  1987年   813篇
  1986年   732篇
  1985年   896篇
  1984年   1003篇
  1983年   933篇
  1982年   913篇
  1981年   823篇
  1980年   781篇
  1979年   711篇
  1978年   706篇
  1977年   635篇
  1976年   582篇
  1975年   586篇
  1974年   553篇
  1973年   586篇
  1972年   399篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
341.
342.
This work briefly discusses the main features of probabilistic seismic hazard analysis (PSHA). Special attention is paid to the identification and quantification of uncertainties related to seismic source characteristics and seismic engineering models for prediction of strong ground motions. The principal seismic models and the results of PSHA application for detailed seismic zoning of urban territories in Sakhalin Island are presented.  相似文献   
343.
The complex variables boundary element method (CVBEM) is used to study interaction between a circular opening and fractures originating from its boundary in a piecewise homogeneous plane. A new complex hypersingular equation for piecewise homogeneous media with a circular opening is obtained. The equation is solved using the CVBEM technique with circular and straight boundary elements and polynomial approximations (with square root asymptotics for crack tip elements) for the unknown functions. The algorithm is verified through comparison with known semi‐analytical and numerical solutions that involve interaction between a circular opening and specific systems of cracks or other openings. New numerical results concerning the interaction of the circular opening with the cracks and circular inclusions are presented. The method is applied to an important problem in the petroleum industry: modelling propagation of hydraulic fractures in the vicinity of a borehole. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   
344.
We examine the various types of mineral waters occurring on the projected specially protected transboundary natural territory “Istoki Amura”, on the Hentei-Dauria neotectonic high. We suggest the pattern of rational utilization of the mineral springs according to the nature conservation status of the terrain (nature reserves, national parks, and public access areas).  相似文献   
345.
Doklady Earth Sciences - Analysis of observations of the Earth’s rotational velocity and volcanic activity of the planet from 1720 until 2015 suggests that higher volcanic activity temporally...  相似文献   
346.
347.
348.
349.
Palaeomagnetism of Holocene lake sediments from north Poland   总被引:1,自引:0,他引:1  
Summary. Detailed palaeomagnetic investigations of 17 cores of Holocene lake sediments from four lakes in Poland show a pattern of declination variations similar to those found in Lake Windermere, England and in addition a well defined pattern of inclination variations. A total of nine inclination swings are observed compared to five declination swings and their phase relationships are such that both sets of swings cannot be periodic. Exact dating of the palaeomagnetic record is not possible as radiocarbon ages are over 1000 yr older than those deduced from palynological studies. Thermomagnetic and X-ray studies on magnetic concentrates confirm the results of studies of remanence cooling, IRM acquisition and coercivity experiments which are consistent with fine grained magnetite as the main magnetic mineral in the sediments.  相似文献   
350.
Visual Interpretation of LANDSAT imagery of Eastern Ghats-Godavari delta area on scale 1:1,000,000 on spectral bands 5 and 7 was attempted. A neotectonic and geomorphic map was prepared from these images showing among other features major and minor lineaments. The importance of some of these lineaments for sedimentation, oil migration and localisation of ore bodies is discussed.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号